Inhibitory effect of colchicine on the iron transport and the release system in rat incisor ameloblasts: An ultrastructural study.

Abstract

The present study was pursued to investigate the effects of colchicine on the iron transport and the release process in ameloblasts of the rat incisor by electron microscopy. Male Wistar rats, 120 g body weighing on average, were injected intravenously with colchicine at a dose of 1.0 mg/kg and sacrificed at intervals of 8, 16, and 24 hours. The control rats received physiological saline of the same injected volume as colchicine. Ultrastructural observations of the ameloblasts were performed from the pigment release stage to the regression stage. In the controls, the iron-containing pigment granules were found to be distributed mainly in the middle part of the ameloblasts and their number gradually decreased from the pigment release stage to the incisal end. Within 8 hours after the colchicine injection, the number of pigment granules increased and they accumulated in the middle and distal part of the cell. The nucleus moved toward the distal direction. These findings were more remarkable at 16 and 24 hours. The shape of the ameloblasts were transformed to a rounded profile and many vacuoles appeared in the proximal portion of the cytoplasm. Further, the cytoplasmic microtubules decreased in number. Colchicine seemed to inhibit the iron transport and the release process in the ameloblasts by interrupting the digestion system of the pigment granules and/or the release process of iron from pigment granules. These observations suggest that the cytoplasmic microtubules are important for the regulation of the transport and the release of iron in the rat incisor ameloblast.